Faulty network switched closed Melbourne tunnels

Traffic storm begat traffic chaos

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Private road operator Transurban says a faulty network switch was to blame for a computer fault that crippled Melbourne’s traffic network early in October.

The 12-hour shutdown of two key tunnels in Melbourne, the Burnley and Domain tunnels, caused 20 km worth of gridlock. At the time, the company blamed a computer glitch.

The company has now released (PDF) the results of its investigation into the incident, blaming a network switch failure. Without naming the vendor involved, Transurban says the faulty switch caused a broadcast storm, and that the parallel backup switch failed to “operate as designed on the day”.

“Our investigation has identified a network switch failure that caused a broadcast storm. A broadcast storm creates countless transmissions, which, in the case of CityLink, utilised all the available computer capacity within the IT network. This rendered our tunnel safety systems, among others, ineffective,” CEO Scott Charlton says in the company’s statement.

The hardware failure at 4.30 am shut down the company’s safety systems, and at 5.30 am, the company decided to close the tunnels. The affected safety systems include emergency response, radio transmission systems, signage, smoke exhaust and water deluge.

Transurban has issued a statement saying that it identified the failed switch on the day of the incident, and has emphasised that its investigation “has not identified any external interference with the IT network”.

The company has brought forward a systems upgrade scheduled for 2014 and including the replacement of its network switches, to commence immediately. ®